(a) Field of the Invention
The present invention relates to a pusher in an autohandler for pressing a semiconductor device and, more particularly, to a pressing device used in an autohandler for pressing a semiconductor device to allow electrodes of the semiconductor device to contact respective pins of a socket during testing the electric characteristics of the semiconductor device.
(b) Description of the Related Art
Measurement of electric characteristics of a semiconductor device, or semiconductor integrated circuit, is performed using an autohandler and a socket having a plurality of socket pins. The autohandler includes a pusher for pressing the semiconductor device from the top surface thereof toward the socket to allow the electrodes of the semiconductor chip to mechanically and electrically contact the socket pins, for measurement of the electric characteristics of the semiconductor device.
FIG. 7 is a schematic sectional view showing the locational relationship between the autohandler and the semiconductor device.
The autohandler 60 shown in FIG. 7 includes a pusher 61 and an inserter 62, and handles a packaged semiconductor device 63 for measurement of the electric characteristics thereof. The semiconductor device 63 carried by the inserter 62 is pushed or pressed in the direction “A” by the pusher 61 toward the socket 65, thereby allowing the bottom electrodes 64 of the semiconductor device 63 to contact the respective socket pins 66 of the socket 65.
The requirements for the pusher 61 of the autohandler 60 include a uniform pressure being applied onto the top surface of the chip of the semiconductor device 63, i.e., device under test (DUT). The techniques for applying a uniform pressure onto the surface of the semiconductor chip include one used in the field of mechanical polishing of the semiconductor chip by using a polishing head. In this technique, an elastic pressure film is interposed between the chip and the polishing head, and a fluid pressure is applied via the elastic pressure film onto the semiconductor chip in order to press the chip toward a table. This technique utilizes the principle that the elastic pressure film expands under the fluid pressure. Such a technique is described in JP-A-2001-113457, for example.
The structure of the pusher 61 shown in FIG. 7 suffers from a problem as described hereinafter. If the semiconductor device 63 shown in FIG. 7 is a hybrid semiconductor device including a plurality of semiconductor chips, such as including DRAM and SOC chips, and thus has a significant step difference on the top surface thereof, the pusher 61 should have a shape adapted to the step difference. This may be achieved, as shown in FIG. 8, by designing a new pusher 61A having a front surface adapted to the step difference formed between the chip 65a and the chip 65b of the semiconductor device 63. However, such semiconductor devices may have a range of variation in the step difference, and thus render the pressure applied to the semiconductor device by the new designed pusher 61A to be ununiform as a whole.
In addition, since there are differences in the chip size between the types of devices, e.g., between the all-purpose semiconductor device such as a TSOP (thin small out-line package) device and the BGA (ball grid array) device or CSP (chip size package) device, a dedicated pusher is generally used for each of the respective types of the devices. This increases the man power for design and manufacture of the pusher, thereby increasing the TAT and cost of the semiconductor devices.
With reference to FIG. 9, there is shown that another autohandler 60A is used to measure the electric characteristics of a plurality of semiconductor chips 66a to 66c of the same type, however, having different thicknesses due to variation of the thickness. In such a case, since the pushers 61a to 61b advance a constant distance for pressing the semiconductor chips 66a to 66c, the loads applied to the semiconductor chips 66a to 66c differ from one another depending on the difference in the thickness of the chips 66a to 66c. 
In the technique described in the above patent publication, it is not considered to apply a uniform load to a plurality of types of semiconductor chips having different thicknesses. Thus, the described technique cannot apply a uniform load onto the semiconductor device having thereon a step difference due to different thicknesses of the chips. In particular, since the elastic pressure film has suction holes thereon, the described technique cannot be applied to a pusher for pressing the semiconductor device including a plurality of chips having different thicknesses.